vim-patch:8.2.3627: difficult to know where the text starts in a window

Problem:    difficult to know where the text starts in a window. (Sergey
            Vlasov)
Solution:   Add the "textoff" entry in the result of getwininfo().
            (closes vim/vim#9163)
https://github.com/vim/vim/commit/cdf5fdb2948ecdd24c6a1e27ed33dfa847c2b3e4

Fix indent in Test_getbufwintabinfo().

vim-patch:8.2.{3468,3617,3618,3622}: some other CWD related patches

* send vim.NIL instead of not sending workspaceFolders
* read fallback rootPath and rootUri from workspaceFolders
* update documentation

Problem:    getcwd() is unclear about how 'autochdir' is used.
Solution:   Update the help for getcwd().  Without any arguments always return
            the actual current directory. (closes vim/vim#9142)
https://github.com/vim/vim/commit/851c7a699ae00bdc14a4db874cf722b7b7393b53

See:

- https://emmylua.github.io/annotations/param.html
- https://emmylua.github.io/annotations/return.html

Problem:    No event is triggered when closing a window.
Solution:   Add the WinClosed event. (Naohiro Ono, closes vim/vim#9110)
https://github.com/vim/vim/commit/23beefed73aadb243fb67cf944e3d60fe8c038bb

Nvim has already implemented this feature, so this only changes tests
and docs.

Problem:    Cannot use \x and \u when setting 'listchars'.
Solution:   Support hex and unicode in hex form. (closes vim/vim#9006)
https://github.com/vim/vim/commit/93ff6720fe4427341bc426b6d46e6324f226c270

Update runtime files
https://github.com/vim/vim/commit/519cc559b08b800edc429688aece7ad6a00d41eb